pub fn odd_fibnacci_sum(threshold: u32) -> u32 {
    let mut first = 1;
    let mut second = 1;
    let mut sum = 0;
    while second < threshold {
        if second % 2 == 1 {
            sum += second;
        }
        let t = first + second;
        first = second;
        second = t;
        
    }
    // println!("threshold: {}, sum: {}", threshold, sum);
    sum + 1
}
